How Does a Furnace Work?

You’d be amazed how many times people sheepishly ask us this question!  If you don’t know how your furnace works, that’s completely okay.  It’s not as if everyone are as experienced with the workings of a furnace as we are.

When people say “furnace” what they are typically referring to is the system in place that heats their home.  While your furnace is likely sitting down in your utility room (commonly called a “furnace room”), know that the system that heats your home is actually a combination of appliances that work in conjunction with one another.

A Typical Home Heating & Cooling Setup

Most homes will have a standard HVAC setup, with a furnace and a thermostat.  The thermostat measures the temperature of the ambient air surrounding it.  When it reads an air temperature lower than what it has been set to regulate, it sends a signal to the furnace to turn on.

The two most common types of furnaces found in British Columbia are natural gas and electrically powered.  Once the furnace has received the signal from the thermostat to turn on it will take in air via its intakes (called “cold air returns”, found throughout the home), heat the air up, and then send it throughout your home via the duct system.

Another Common Heating & Cooling Setup

Nearly all homes in BC have the thermostat/furnace combo (save for homes that are climate controlled through other mechanisms, such as radiators, baseboard heating, solar heating, or otherwise).  However, many homes also have a humidifier and an air conditioner.  Some may even have an advanced air filtration system (common if you suffer from seasonal allergies).

Other home comfort appliances your home may have in addition to your furnace:

  • A humidifier – Used to keep your indoor air at a consistent humidity, a humidifier can greatly improve your indoor air quality.  If your home has wood furniture, hardwood floors, or solid wood cabinets, your home may require a humidifer to ensure those items do not dry out (which can cause cracking, warping, and other undesirable effects).
  • Central air conditioning – Just as a furnace warms your indoor air, your air conditioner will cool it.  Read more about how an air conditioner works.
  • Advanced air filtration – While nearly all furnaces will have some kind of furnace filter installed, many homes will add an advanced air filtration setup to further filter indoor air.  If you suffer from sever allergies, have a lot of pets, or just want really clean air, you may want to consider investing in one.

Okay, So Now You Know What’s In Your Home.  Now It’s Time to Learn About How a Furnace Works.

Let’s pretend that you have your thermostat set to  22°C.  Your thermostat will regulate the air temperature by engaging your furnace or air conditioner as required in order to keep the air at a consistent temperature.

When your thermostat tells your furnace to engage, the following things typically happen:

  • The furnace receives the signal to turn on – Many thermostats make a click when the signal has been sent.
  • Fuel is sent to the burners – Like your BBQ, the heart of your furnace are gas burners (or a heat coil if you have an electric furnace).  These ignite and begin producing heat.
  • Internal sensors verify that all the burners are actually lit – This is a safety mechanism designed to ensure that no natural gas is being dispersed without being burned (hint: that’s bad).
  • The burners heat your heat exchanger – A heat exchanger more efficiently warms air compared to just the burners doing their thing.
  • Your blower motor engages and begins to circulate air – This air passes through the heat exchanger and is then sent throughout the duct system in your home.

Modern high-efficiency furnaces are far better at doing their jobs than furnaces from just 10 years ago.  If you’re noticing higher utility bills than normal, and there is nothing wrong with your furnace, you may want to consider upgrading to a new high-efficiency furnace.  Hey, we do that!